1. Field of the Invention
The present invention relates an X-ray CT imaging device for, for example, detecting X-ray output from an X-ray generator by use of an X-ray detector and thus performing X-ray CT imaging of a subject which is located between the X-ray generator and the X-ray detector.
2. Description of the Prior Art
Conventionally in the field of medicine and the like, X-ray CT imaging is performed. According to the X-ray CT imaging, a subject is irradiated with X-ray to collect projection data, and the obtained projection data is reconstructed on, a computer to generate a computerized tomography image (computed tomography (CT) image, volume rendering image, etc.).
Such X-ray imaging is performed as follows. In the state where a subject is located between an X-ray generator and an X-ray detector, a cone-like X-ray beam (X-ray cone beam) is directed from the X-ray generator to the subject while the X-ray generator and the X-rat detector are revolved around the subject. X-ray detection results (projection data) are collected by the X-ray detector, and three-dimensional data is reconstructed based on the collected X-ray detection results (projection data). An example of device for performing such X-ray CT imaging is disclosed in, for example, Patent Document 1.
Patent Document 1 describes that the X-ray imaging device described therein can perform CT imaging of a wider area with a smaller X-ray detection plane by offset scanning. According to the offset scanning, the position to which the X-ray cone beam is directed is offset from the center of the subject, so that a part of the subject is always irradiated with the X-ray cone beam during the imaging.
However, the X-ray imaging device described in Patent Document 1 has the following undesirable possibility. The X-ray expands in a length direction, which is a direction of the axis of revolution, in a uniform manner. Therefore, an area of the subject which is not an area of interest is irradiated with the X-ray to unnecessarily increase the amount of exposure, or the area of interest cannot be irradiated with the X-ray.